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Rh Yet, there has been very little field exploration in the heart of the area so that its vacuity may be more apparent than real. Such collections as have been made contain the grooved



hammer, chipped scrapers, points, and the bone implements found among the historic tribes.

Among the most striking features are the great quarries of quartzite in the valley of the Platte, Wyoming, where tracts many acres in extent show deep and extensive diggings for